1. Field of the Invention
The present invention relates generally to superchargers for providing increased airflow to the engine of a motorcycle, such as a V-twin engine typically found on a Harley-Davidson® motorcycle. More specifically, the present invention concerns an improved drive assembly that compactly spans the drive train components of the motorcycle while remaining entirely inboard of, and thus does not interfere with, the rider's anatomical engagement with the motorcycle. The unique drive assembly enables the supercharger to be positioned in the otherwise unused space in the fore area of the motorcycle chassis and can be driven off of a breakaway power take-off drivingly communicating with a selected component of the generally aftward drive train of the motorcycle.
2. Discussion of Prior Art
It is known in the art to supercharge an internal combustion engine to provide increased airflow to the engine to thereby enhance the power output of the engine. There are several types of superchargers known in the art, including, for example, Roots-type superchargers and centrifugal superchargers, both of which are driven off of the crankshaft of the engine, as well as turbochargers that are driven off of the engine's exhaust. One exemplary centrifugal supercharger well advanced in the art and particularly resistant to failure is disclosed in the copending U.S. application patent Ser. No. 10/641,619 entitled CENTRIFUGAL COMPRESSOR WITH IMPROVED LUBRICATION SYSTEM FOR GEAR-TYPE TRANSMISSION, filed Aug. 14, 2003 (the “Jones '619 application”), having a common inventor and assignee with the present application and hereby incorporated by reference herein.
It is also known in the art to supercharge a motorcycle engine, including the distinctive V-twin engine design found on Harley-Davidson® motorcycles. However, motorcycle engines and particularly Harley-Davidson® V-twin motorcycle engines provide several problems for supercharging applications. For example, superchargers are typically driven off of the engine's crankshaft, however, the crankshaft is typically positioned adjacent the footboard and foot controls of the motorcycle and therefore there is very limited space in and around the crankshaft in which to position drive components. Therefore, in order to place the drive components and/or the supercharger itself in the crowded area around the crankshaft, the components can undesirably alter or interfere with the rider's otherwise normal, comfortable operating position and/or the rider's ability to readily manipulate the foot controls. Additionally, it has been determined that Harley-Davidson® owners in particular are loathe to modify their motorcycles in any way that will materially alter or affect the original distinctive appearance and sound of the motorcycle. Furthermore, prior art superchargers, particularly superchargers that do not utilize multiple bearing arrangements or a self-contained dedicated lubrication system, can be subject to premature failure, or failure prior to the life expectancy of the motorcycle's engine, particularly where the drive assembly is not maintained within very tight tolerances. Failure of these prior art superchargers can be problematic as it may in turn cause catastrophic, and thus costly, engine failure as well. The potential for such engine failure is exacerbated where the supercharger is directly integrated with the engine, such as sharing a common lubrication system, as foreign debris occasioned by supercharger failure can leak into the internal components of the engine. It has recently been determined that these problems are exacerbated by the large degree of “slop” associated with the flywheel, thus limiting the prior art superchargers to direct drive systems that take power directly off of the crankshaft. Some of these problems, as well as others, associated with supercharging a V-twin motorcycle engine are discussed in U.S. Pat. No. 6,105,558 entitled SUPERCHARGING APPARATUS, issued Aug. 22, 2000.
All prior art supercharged motorcycles, including the supercharging system disclosed in the '558 patent, are problematic and subject to several undesirable limitations. For example, all prior art superchargers are driven directly off of the crankshaft and accordingly require drive components, and in most cases, the supercharger housing itself, to be positioned on, above, and/or outboard of the crankshaft. Such positioning is undesirable as these components project into the leg-receiving area of the motorcycle where the rider's legs would otherwise be located during normal operation thereby interfering with the rider's comfort and operation of the motorcycle. Additionally, such positioning undesirably alters the otherwise smooth aesthetic look of the already crowded engine and crankshaft area. Accordingly, there is a need for an improved supercharger system for a motorcycle that does not interfere with the rider's normal operating position or materially alter the overall appearance and sound of the motorcycle and does not cause engine damage in the event of a catastrophic failure of the system.